The modern communications era has brought about a tremendous expansion of wireline and wireless networks. Computer networks, television networks and telephony networks are experiencing an unprecedented technological expansion, fueled by consumer demand. Wireless and mobile networking technologies have addressed related consumer demands, while providing more flexibility and immediacy of information transfer.
Current and future networking technologies continue to facilitate ease of information transfer and convenience to users. In order to provide easier or faster information transfer and convenience, telecommunication industry service providers are developing improvements to existing networks. For example, the Evolved Universal Mobile Telecommunications System (UMTS) Terrestrial Radio Access Network (E-UTRAN) is currently under development. The E-UTRAN, which is also known as Long Term Evolution (LTE), is aimed at upgrading prior technologies by improving efficiency, lowering costs, improving services, making use of new spectrum opportunities, and providing better integration with other open standards. A number of these new networking technologies include packet-switched (PS) networks, such as the 3rd Generation Partnership Program (3GPP) IP Multimedia Subsystem (IMS) network, which has adopted the Session Initiation Protocol (SIP) as the signaling protocol.
As these new networking technologies are deployed, coverage by the new networking technology may not be universal. In order to assure quality of service and avoid dropping of calls, the new networking technologies may be configured to coexist with legacy networking technologies, such as circuit-switched (CS) networks. In this regard, a mobile terminal (for example, user equipment—UE) may be handed over between, for example, an LTE network and a CS network. Single radio voice call continuity (SRVCC) functionality is being defined to enable a UE to perform an inter-domain handover from LTE to CS such that a voice over Internet Protocol (VoIP) session over IMS over the LTE access may be transferred to the CS network, such as when the LTE coverage is lost.